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THE rNSTITUTE OF INDUSTRJAJL RESEARCH 



THE PRESERVATION 

OF THE 

EXTERIOR OF WOODEN BUILDINGS 



ALLEJRTON S CUSHMaN Director 

TBE INSTITUTB OP IKHUSTKUI RBSBARCH 

HENRY A. GARDNER. Asst. Director 

IK CHARGE DIVISION OP fAiNT TBCRNOLOOY. 
Tae INSTITUTE OP INDUSTRIAL RESEaRCB 




WASHINGTON 
19H 



THE INSTITUTE OF INDUSTRIAL RESEARCH 



Allerton S. Cushman, a. M., Ph. D., Director ^ In Charge 
Division Metallurgical Problems. 

Henry A. Gardner, Assistant Director, In Charge Division 
of Paint Technology. 

N. Monroe Hopkins, Ph. D., In Charge Division of Elec- 
trical Engineering and Electrochemistry. 

Chas. a. Crampton, M. D., Ph. G., In Charge Division of 
Food and Drug Products. 

G. W. Coggeshall, Ph. D., In Charge Division of Mill 
Proble?ns. 

Chas. BASKERviLtE, Ph. D., F. C. S., In Charge Technology 
of the Rarer Elements. 



Copyright, 1911, The Institute of Industrial Research. 



lULLETIN No. 1 



lHh; INbTITUTKOK INDUSTRIAL RESEARCH 



\'M PRESERVATION 



OF THE 



EXTORIOK OF WOODEN BUILDINGS 



ALLERTON S CUSHMAN Director 

THE INSTITUTE OF INDllSTKiAl RESEARCH 

HENRY A GARDNER. Asst. DrRECTOK 

IN CHARGE DIVISION OF HAINI TECHNOLOGY. 
THE INSTITUTE OF INDUSTRIAL RESEARCH 







WASHINGTON 
1911 






O ^ 






WASHINGTON, D. C. 

PRESS OF JUDD & DETWEILER, INC. 

1911 






J 



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2. 



PREFACE 



FOR a number of years the writers 
have been making a study of indus- 
trial problems and have been publishing 
the information which they have ac- 
quired, regarding the value of various 
structural materials, for the benefit of 
consumers as well as producers. The 
Institute of Industrial Research has re- 
ceived so many requests recently for 
information in regard to just what paints 
should be selected for the protection and 
decoration of houses and other buildings 
lliat it has seemed best to sum up the 
suljject in the form of a special pamphlet 
or bulletin. It is only after years of 
investigation work carried on by the 
authors, both separately and in co-opera- 
tion, that any review of the work has 
seemed possible, for only recently have 
the results of tests carried on in a num- 
ber of different localities seemed to jus- 
tify a definite opinion in regard to the 
best selection of exterior paints. No 
attack on any one paint material is here 
included, but the value of each has been 
carefully weighed, and the attempt is 
3 



made to discuss them in the light of ex- 
perience and knowledge. It is the au- 
thors' intention in this bulletin to put 
into the hands of architects and paint- 
users who may not be thoroughly famil- 
iar with the technical properties of paint 
materials, information which will enable 
them to make a proper and intelligent 
selection of paints for the preservation 
and decoration of the exterior of wooden 
building^s. 



The Preservation of the Exterior of 
Wooden Buildings 



Lumber and its Relation to Paints: 
The proper choice and treatment of lum- 
ber is one of the most important prob- 
lems which the builder as well as the 
painter has to face. When about to build 
a dwelling, barn, or other structure made 
principally of wood, the question is sure 
to arise in regard to what variety to se- 
lect so as to get the maximum service 
and money value. The locality in which 
the structure is to be built must often 
have a bearing upon this question. While 
it is true that the painting of each type 
of wood demands the special considera- 
tion of the painter, it is also true that 
the study of paints for wood protection 
points toward the production of a paint 
that will give satisfactory results under 
all conditions and on all grades. It is 
the writers' opinion that a paint may be 
made that will be perfectly well suited 
for the preservation of every species of 
wood, provided the paint is properly 
treated in the hands of the skillful and 
intelligent painter, who can produce last- 
ing results on almost every type, by 
varying the proportion of thinners and 
oil in the various coats. The painter 
who vises the same paint on soft pine^ 

5 



and again on hard pine, without making 
a special study of how to reduce the 
priming coat for the hard pine, will be 
likely to get inferior results on the latter. 
In case of failure, the natural impulse is 
often to place the blame upon the paint, 
whereas the real responsibility may rest 
u])on the painter's lack of knowledge. 

Signs of Paint Failure: Those who 
are responsible for the care and mainte- 
nance of property are familiar with the 
condition of surface presented by almost 
all wooden buildings or structures which 
have been improperly painted with infe- 
rior paints. "Chalking" or "flouring" 
are terms used to describe the condition 
of a paint surface which has deterio- 
rated within the paint film. The forma- 
tion of minute fissures, generally spoken 
of as "checking," as well as the effects 
best described as cracking, scaling, peel- 
ing, and blistering, are other signs of 
failure which cause paint coatings to 
present an unsightly appearance, and 
which point inevitably either to the use 
of improperly made paints or to im- 
proper application. The cause of these 
conditions is not difficult to understand 
when even a brief study of the character 
of the materials entering into the com- 
position of a paint has been made. It 

Note. — For a more detailed account of the 
lumber question, see "Modern Lumber as a 
Problem for the Painter," read by John Dewar, 
at the Convention of Master House Painters' 
and Decorators' Association of Pennsylvania, 
January, 191 1, Pittsburg, Pa. 



n 




BLISTERING.— Type of Decay Exhibited by Improperly 
Made Paint (magnified view). 














«'^^*^ 



'^■■ 




« 







CHALKING.— Type of Decay Exhibited by Improperl 
Made Paint (magnified view). 




CHECKING.— Type of Decay Exhibited by Improperly 
Made Paint (magnified view). 




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TRACKING.— Type of Decay Exhibited by Improperl] 
Made Paint (magnified view). 




SCALING.— Type of Decay Exhibited by Improperly 
Made Paint (magnified view). 




GENERAL DISINTEGRATION.— Type of Decay Ex- 
hibited by Improperly Made Paint (magnified view). 



is, however, a fortunate circumstance 
that the proper admixture of different 
types of pigments enables us to correct 
the strong tendency exhibited by special 
pigments to rapidly deteriorate in an oil 
film. This point will be more fully dis- 
cussed in a later paragraph. 

Requisites of a Good Paint: Progress- 
ive manufacturers are aiming to produce 
a paint which will show, under the 
widest range of conditions, good hiding 
power, adhesiveness, freedom from in- 
ternal strains, permanency of color, rela- 
tively high imperviousness to moisture, 
sufficient elasticity to prevent scaling or 
cracking when subjected to expansion 
or contraction, and freedom from the 
chemical action which results in deep 
checking or excessive chalking. Such a 
product as this cannot be attained, in 
the writers' opinion, by the use of any 
one pigment in linseed oil. In order to 
meet all the demands as stated above, 
there should be in an economical and 
durable paint a proper percentage of the 
various pigments which, united, will tend 
to correct each other's faults, and thus 
produce a durable paint coating of maxi- 
mum efficiency. 

The Composition of Paints: As is well 
known, a paint is a mixture of one or 
more pigments and a vehicle which acts 
the part of the spreading and binding 
medium. Up to the present time the 
vehicle portion of paints has generally 
been made of linseed oil, admixed with 
some volatile thinner, such as turpentine. 

13 



The subject of oils and paint vehicles 
will be discussed more fully later on. 

Physical Properties of Pigments: The 
pigment portion of a paint for use on 
barns and farm buildings may, if de- 
sired, be composed of properly selected 
iron oxides or other colored pigments, 
even containing in some cases a moder- 
ately high percentage of silica, clay, or 
other inert materials, and give perfectly 
satisfactory results. For the preserva- 
tion and decoration of dwellings, how- 
ever, the pigment portion of paints is 
generally made as a whole or in part of 
the more expensive white pigments, such 
as white lead and zinc oxide. The rela- 
tive values and properties of these white 
base pigments will now be taken up. 

White Leads: White lead, either of 
the corroded or sublimed type, is per- 
haps the most generally used of all the 
white pigments as a paint base. Cor- 
roded white lead is a basic carbonate of 
lead, while sublimed white lead is a basic 
sulphate of the same metal. Both of 
these types are white, and admirably 
adapted as painting materials. They 
take relatively the same amount of oil 
and spread easily, producing paint films 
which are highly opaque and which, 
therefore, hide efficiently the surface 
upon which they are placed. Sublimed 
white lead is a relatively finer pigment 
than corroded white lead, and seems to 
show a tendency to chalk to a greater 
extent upon exposure to the weather. 
Corroded white lead is more alkaline, 
however, than sublimed white lead, and 
14 



when used alone with linseed oil gen- 
erall}^ shows a tendency to chalk to a 
considerable extent in a short time and 
to show deep checking, thus permitting 
the admission of moisture. The alkaline 
nature of this pigment produces con- 
siderable action upon certain tinting 
colors and results in fading or darken- 
ing, when mixed with delicate greens or 
blues. 

The use of white lead has been con- 
demned in some parts of this country, 
as well as abroad, because of its alleged 
poisonous properties. While it is true 
that lead poisoning may occasionally 
occur in some factories where the work- 
man and his conditions are not properly 
safeguarded, it is, nevertheless, a fact 
that lead poisoning very seldom occurs 
among painters of experience and cleanly 
habits. Carelessness in mixing white 
lead is, fortunately, a practice almost 
obsolete among modern painters. The 
use of paints already ground in oil by 
means of machinery to a pasty condition, 
allowing easy working and reducing, 
obviates the danger of lead poisoning 
from any such cause as this, even though 
the percentage of lead in such paints is 
in preponderance. Recent efforts that 
have been made by the legislatures of 
certain States to brand lead paints as 
poisonous are not only unnecessary, but 
show a complete ignorance of the prob- 
lem. 

Zinc Pigments: Another pigment which 
has proved itself of great value to the 
15 



painter is zinc oxide, ^he use of this 
pigment may be said to have almost 
revolutionized the paint industry- of the 
world, and its increased consumption 
during the last ten years is sufficient evi- 
dence of its value as a painting material. 
Zinc oxide is produced by oxidation and 
sublimation of zinc ores and is not only 
extremely fine, but of great whiteness. 
It has good hiding power, although not 
quite so great as that shown by the white 
leads. It tends to produce a glossy sur- 
face, making it especially valuable for 
use on interior work and in enamels. 
When used alone it has the effect of 
hardening the oil film in which it is en- 
veloped, and upon long exposure causes 
cracking and scaling. However, when 
the sublimed or corroded white leads are 
properly combined with zinc oxide, a 
more durable surface is produced, the 
shortcomings of each pigment being 
overbalanced by the good properties of 
the other. The proper combining prop- 
erties of zinc oxide with white lead may 
be said to vary between 20 to 55 per cent 
of zinc oxide for paints designed for ex- 
terior use. In the opinion of the authors, 
lead and zinc pigments in the above per- 
centage, properly blended and ground, 
make paints of far better wearing value 
than can be produced with either white 
lead or zinc oxide used alone. 

Zinc Lead: Zinc lead, a pigment sub- 
limed from mixed lead and zinc ores, 
and containing about equal proportions 
of zinc oxide and lead sulphate inti- 
16 



mately combined, as well as leaded zinc, 
a product similarly produced, but with 
the zinc oxide running about 75 per cent, 
are white base pigments of value, which 
are used to a considerable extent. They 
are generally slightly ofif color, however, 
and are therefore used most largely in 
paints which are to be tinted in various 
colors, 

Lithopone: Lithopone, a pigment pro- 
duced by precipitation, and consisting of 
zinc sulphide and barium sulphate, is of 
great value in the manufacture of inte- 
rior paints. On account of its liability 
to darken and disintegrate, however, it 
is seldom used on exterior work, al- 
though recent tests have shown that 
when used in combination with zinc 
oxide and whiting, it gives very promis- 
ing results. 

Crystalline Pigments and Their Use: 
Barytes (barium sulphate), silex (silica), 
whiting (calcium carbonate), gypsum 
(calcium sulphate), asbestine (silicate of 
magnesia), and china clay (silicate of 
alumina) are white crystalline pigments 
which, when ground in oil, become trans- 
parent. All of these pigments possess 
the property of strengthening a paint film 
made of white lead and zinc oxide, and 
often increase the durability of such a 
paint. Barytes, silica, and china clay are 
especially valuable for this purpose. As- 
bestine, because of its needle-like struc- 
ture and low gravity, prevents settling 
and acts as a reinforcer of paint films. 
Whiting or calcium carbonate should b^ 

17 



used when zinc oxide is in excess in a 
paint, so that the hardness of the paint 
may be overcome. 

A white paint must be possessed of 
sufficient opacity to efficiently hide the 
surface upon which it is placed, when 
three coats are applied for new work or 
two coats for repainting work. Mixtures 
of the- white leads and zinc oxide, with 
the latter pigment running not over 55 
per cent, will easily produce such a 
result and wear well. It is generally 
deemed advisable, however, by most 
manufacturers to take advantage of the 
excessive opacity of such mixtures, 
which allows the introduction of moder- 
ate percentages of those inert pigments 
which give greater strength and other 
desirable features to a paint. The per- 
centage of natural crystalline inert pig- 
ments to add to a white paint made of 
lead and zinc must, however, be moder- 
ate and insufficient to detract materially 
from the hiding power of the paint.* 



* Pigments such as silica, barytes, china clay, 
and asbestine are thoroughly inert. Recent in- 
vestigations have proved that they accelerate 
the drying of linseed oil, but this is not due to 
any chemical action they exert, but rather to 
their physical action in distributing the mass of 
oil in which they are ground, and thus allow- 
ing a greater surface to be exposed to the 
oxygen of the air. 

It is also possible that some of the inert pig- 
ments may stimulate oxidation by catalytic or 
contact action, although they are not chemi- 
cally active in themselves. 



iS 



II 



White-Paint Formulas: From these 
conclusions, which have come from wide 
experience in the testing of paints under 
actual service conditions, there can be 
recommended to the buyer of paints and 
to the manufacturer and master painter 
tliose machine-mixed paints in white, 
made by reputable manufacturers, the 
composition of which will show a mix- 
lure of white lead and zinc oxide, with 
the latter pigment within limits of be- 
tween 15 to 55 per cent, and especially 
the same mixtures reinforced with the 
moderate percentage of crystalline inert 
pigments referred to above. 

Tinted paints possess greater hiding 
power than white paints, and the above 
proportions would be somewhat changed 
for a tinted paint containing any per- 
centage of coloring material. Tinted 
paints are, moreover, far more service- 
able than white paints, as will be shown 
later. 

Adill vs. Paddle: The mixtures under 
consideration should be ground in linseed 
oil by the manufacturer, through stone 
or steel mills, to a very fine condition, 
as it is only through proper grinding that 
the pigments can be properly blended. 
The mixing of paint by hand is, fortu- 
nately, to a large extent a thing of the 
past. The uneven lumping of hand- 
mixed paints is often the cause of their 
failure. Such ancient and crude practice 
should be avoided by every painter, for 
it is more economical to obtain semi- 
paste paints, properly ground by ma- 
19 



chinery, to such a condition that they 
may be easily broken up and tempered. 
Such paints may be reduced to the proper 
consistency with oil and volatile thinner 
for application to any kind of wood. 

In the opinion of the writers, a ma- 
jority of the paints sold by reputable 
dealers and made by reputable manufac- 
turers in this country are not only made 
from the best linseed oil and highest- 
grade pigments obtainable, but are put 
up in a form ready for the painter to 
thin down with full oil or turpentine re- 
ductions, either for priming work or to 
be used without reductions for finishing 
coats. The large metropolitan painter 
who wishes to make his own tints and 
shades may, however, prefer to have his 
mixed pigment paint ground by the 
manufacturer in heavy paste form for 
certain purposes. 

Results of Field Tests: A careful 
analysis of the results of field tests which 
have been carried on in different parts 
of the country would be far too volumi- 
nous for insertion in this bulletin. The 
official findings of special committees of 
inspection have already been published 
in special reports. Whereas there may 
still remain ground for some difference 
of opinion in regard to the interpretation 
of the results obtained on the various 
test fences, there can be no doubt that 
considerable information of the highest 
value has been yielded, both to the pro- 
ducers and consumers of paints. One of 
the principal results obtained from these 



tests has led to the opinion expressed 
above by the writers, that better results 
can be obtained by a proper mixture of 
selected pigments than by the use of any 
one pigment in linseed oil. This conclu- 
sion has also been reached by engineers 
of the United States navy, and, as a re- 
sult, the specifications of the Bureau of 
Yards and Docks for paints made of 
straight white lead and oil have recently 
been changed to call for white lead com- 
bined with upwards of 50 per cent of 
zinc oxide. Many engineers and master 
painters have interpreted the results of 
the tests in the same way, and the atten- 
tion of the authors has been called to a 
number of opinions which show that the 
tendency of demand among those who 
are properly informed is for a high-grade 
combination type of paint rather than 
for any single pigment paint. 

Color: The selection of the color for 
a dwelling or other structure is a matter 
that depends largely upon the good judg- 
ment and taste of the owner, combined 
with the advice of the painter. One 
point, however, should be impressed 
upon the mind of both, namely, that 

PRACTICALLY ALL SHADES OR TINTS MADE 
UPON A GOOD WHITE PAINT BASE. 
THROUGH THE USE OF PERMANENT TINT- 
ING COLORS, WILL BETTER WITHSTAND 
EXPOSURE TO THE ATMOSPHERE THAN 
THE WHITE BASE USED ALONE. Owing 
to the cheerful efifect produced by the 
use of white paint on dwellings, a very 
large quantity of white will continue to 
21 



be used. If these white paints are de- 
signed in hne with the suggestions 
brought out above-— that is to say, if the 
white lead bases are properly reinforced 
with zinc oxide and other pigmentary 
materials — better results will undoubt- 
edly be obtained, as far as appearance 
and durability is concerned, than if white 
lead had been used alone. The consumer 
should remember, however, that more 
durable results will be obtained by the 
use of tinted paints. 

Reductions and Thinners: Turpentine, 
with its sweet odor, high solvent action, 
and wonderful oxidizing value, has al- 
ways taken first place among the volatile 
liquids used for thinning paints. Wood 
turpentines, produced from the steam 
distillation of fine - cut fat pinewood 
or from the destructive distillation of 
stumpage and sawdust, have been refined 
in some cases, by elimination of odor and 
toxic effects, to such purity that they are 
equally as good as the purest grades of 
gum turpentine, and their use is bound 
to increase in the paint industry. 

The painter and manufacturer have 
come to understand that certain grades 
of asphaltum and parafBne distillates are 
equally as satisfactory as turpentine for 
use in paints for exterior purposes. 
Those volatile oils which are distilled 
from crude oil with either a parafftne or 
asphaltum base and possessed of boiling 
point, flash point, color, and evaporative 
value approximating similar constants 
of turpentine, are excellently suited to 

jl 



partly, and in some cases wholly, replace 
turpentine in exterior paints. A little 
additional drier added to paints thinned 
with these materials will cause oxidation 
to take place in the proper time. 

Prominent master painters * have 
shown that benzol, a product obtained 
from the distillation of coal tar, differing 
from benzine, a product obtained from 
the distillation of petroleum, is a valu- 
able thinner to use in the reduction of 
paints for the priming of resinous lum- 
ber such as cypress and yellow pitch 
pine. The penetrating and solvent value 
of benzol is high, and it often furnishes 
a unison between paint and wood that 
is a prime foundation to subsequent 
coatings, preventing the usual scaling 
and sap exudations, which often appear 
on a painted surface. Because of the 
great solvent action of benzol, however, 
this material should never be used in the 
second and third coatings. These facts 
will doubtless interest the Southern 
painter, who has so much wood of a 
refractory nature to paint. 

Oils: The increasing cost of linseed 
oil has raised the interesting question as 
to whether or not it is good practice to 
use an admixture of other oils in con- 
nection with it, in high-grade paint coat- 
ings. Strong differences of opinion will 
probably be found in regard to this ques- 
tion, and undoubtedly further investiga- 
tion work is necessary in order to decide 



* Dewar, Titzel et al. 
23 



it. A number of different oils have been 
proposed for the purpose, of which, per- 
haps, soya-bean oil is the one which has 
been most prominently discussed. No 
definite formulas, however, should be 
recommended until the results of investi- 
gations which are now being carried on 
are in hand. A systematic series of test 
panels is now being erected in Washing- 
ton, D. C, on the grounds of The Insti- 
tute of Industrial Research, which are 
designed to gather data covering just this 
point. 

The flax crop conditions have been 
most discouraging during the past two 
years, and the natural shortage of seed 
has caused a rise in the price of linseed 
oil, which has necessitated a rise in the 
price of paint. The added protection to 
be secured, however, through the fre- 
quent application of paint far outweighs 
any increased cost which has been caused 
by the rise in price of the raw commodi- 
ties entering into the composition of 
paint. 



24 



LIBRARY OF CONGRESS 





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